Thermally-responsive electric switch



May 20 1924.

J. TWARDOWSKY THERMALLY RESPONSIVE ELECTRIC SWITCH Filed Dec. 27. 1921 2Sheets-Sheet. l

NIX

Patented May 20: 1924.

UNITED STATES 1,494,650 PATENT OFFICE.

JOHN 'IWARDOWSKY, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS,TO UNIVERSE CORPORATION, OF CHICAGO, ILLINOIS, A CORPORATION OFILLINOIS.

THEBMALLY-RESPONSIVE ELECTRIC SWITCH.

Application filed December 27, 1921. Serial No. 524,991.

To all whom it may concern:

Be it known that I, JOHN TWARnowsKY, citizen of Russia, residing atChicago, in the county of Cook and State of Illinois, have inventedcertain new anduseful Improvements in a Thermally-Responsive ElectricSwitch; and I do hereby declare the following tobe a full, clear, andexact description of the invention, such as will enable others skilledin the art to which it appertains to make and use the same.

My invention relates to electric switches and in one of its generalobjects aims to provide a switch which will automatically be moved toits on and off positions in response to predetermined variations in thepressure of a normally gaseous fluid. In another general aspect, myinvention relates to a thermally responsive electric switching appliancein which the changes in temperature vary the extent to which an inclosedfluid is liquefied, so as to produce corresponding and relatively largechanges in the pressure of the vaporized fluid portion, and

' in which these pressure changes are then utilized for actuating theswitch. Furthermore, my invention aims to provide an electric switchingappliance of the above type or types which will be simple and durable inconstruction, and in which all needed adjustments can be made easily andquickly without taking any portions of the mechanism apart. y

In one of its important commercial applications, the. thermallyresponsive electric switch of my invention is particularly applicablefor use' in controlling the motor which operates the fluid compressor ina mechanical refrigerator of the expansion type. To make such.refrigerators independent of the vigilance of an attendant, it isdesirable that the motor which drives the compressor should be startedwhenever a given temperature is exceeded within the refrigerator, andthat the running of the motor should be stopped whenever therefrigerator has been cooledto a certain degree. Various thermostaticarrangements depending on the expansion of metals wlth an increase oftemperature have been employed for this purpose for controlling themotor in response to such expansion, but these have been unsatisfactoryin practice both owing to the uncertainty of the relays which had to beinterposed between the thermostatically governed control circuit and themotor circuit, and also because of the comparatively slight expansion orcontraction effected in metals within the temperature range desirable inthe refrigerator and of the consequent lack of adequate sensitiveness.

As a substitute for such a thermo-electric arrangement, the appliance ofmy invention first translates the temperature changes into changes inthe pressure of a fluid inclosed in certain passages, part of whichpassages are subjected to the temperature changes within therefrigerator, which my invention employs the resulting pressure changesfor ac.- tuating the switch proper and preferably for directly actuatinga switch controlling the motor circuit.

As part of the equipment for such a purpose, I aim to provide a simpleand easily installed pressure tube adapted to have its the tu'beandhence producing decided pressure changes Within the tube. Then myinvention employs these pressure changes in the fluid for actuating aswitch-throwing lever through the medium of an expansible casing which.forms part of the total passages containing the said fluid. Myinvention also aims to provide a simple mounting for such apressure-responsive chamber, and desirably aims to provide a simplemountin for the entire appliance so arranged at it easily can beattached to any convenient support and so that the main portions of thesame can be rotated to any desired plane without affecting the tightnessof any joints or requiring any changes in the electrical connections.

Moreover, my invention aims to[ provide simple and easily manipulatedmeans for adjusting the fluid pressures at which the switch willautomatically be operated in one direction or the other, therebycorrespondin'gly adjusting the temperature ranges in response to whichthe switch will operate. It also aims to provide a simple, inexpensiveand strong switch construction suitable for this purpose and one inwhich the contacts will be self-cleaning, and aims to provide simplemountings for the various parts and simple means for making thoseimportant adjustments which may be needed for insuring a positive andsensitive action of the throw-over part of the mechanism. Still furtherand also more detailed objects will appear from the followingspecification and from the accompanying drawings in which Fig. 1 is anelevation of a refrigerator, with a portion of its front broken away toshow the mounting of my appliance within the same.

Fig. 2 is an enlarged side elevation of all except the tubular coilportion of the same appliance, showing the switch in its off position.

Fig. 3 is a similar view showing the switch in its on position.

Fig. 4 is a plan view of the same parts, taken with the switch in itsoff position.

Fig. 5 is a side elevation of the head of the switch taken from theright hand of either Fig. 2 or Fig. 3.

Fig. 6 is an enlarged vertical section through the portion of theappliance which transmits the pressure changes to the throwover lever,taken along the correspondingly numbered line in Fig. 4.

Fig. 7 is a perspective View of a fork which forms the base oftheswitch. v In applying my invention for thepurpose of controlling themotor which actuates a mechanical refrigerator, I dispose a fluidcontainer within a cooled chamber of the refrigerator and for thispurpose desirably employ a tube 1 having its major portion.

coiled into a flat'spiral and disposed within a cooling chamber'of therefrigerator 2, the coiling permitting me to expose a large area of tubesurface to the temperature within the said. chamberi This tube 1 is hereshown as closed at. the inner end of its said coiled portion and ashaving its other end threaded into a cup 3 which opens into a diaphragmchamber 4 as shown in Fig. 6. This latter collar 6 on this cup after themanner shown in Fig. 6, it being understood that all joints mentioned bynie may be made fluid-tight by any customary auxiliary means. Thusarranged, the receptacle 4 forms an expansible chamber which will haveits ends flexed away from each other by any increase in internalpressure, and I utilize such a flexing for moving a plunger 7 whichdesirably engages a flat pressure-distributing disk 8 secured to theupper end ofthe re ceptacle 4. The plunger 7 is continuously urgedtowards the said receptacle by a spiral spring 9 interposed between thelower head of the plunger and a bushing 10 threaded into the upperportion 11 of the supporting member of my appliance. This supportingmember desirably includes a'base plate 12 equipped with perforations 13for receiving.

screws by which the sup orting member may be secured to a side 0 therefrigerator or to some other convenient object, the part 11 beingsecured to this base plate 13 by screws 14 and the parts 11 and 13 beingspaced from each other by sleeves 15 through which the screws 14-extend.These sleeves space the said parts sufliciently to provide ample roomfor the expansible receptacle 4 and the pressure-distributing disk 8,and the spacing may also be such that the part 11 acts as a stop forlimiting the upward movement of the disk 8 by the flexing of the closedport, thereby permitting a convenient assembling of the parts and alsofacilitating the adjusting of the position of the switch with respect tothe plunger 7 and the said throw-over connections.

As a simple and highly effective arrangement for this general purpose, Idesirably provide a supporting rod 16 threaded into a portion of thesupporting member (and here shown as threaded into the part 11 of thelatter and extending parallel to the plungers This rod 16 extendsslidably through a bore in a fork 17 which forms the supporting base ofmy switch and which is clamped to the stem by a screw 18. Fastened tothe fork 17 and desirably extending parallel to the stem 16 are a pairof insulating shanks 18 (desirably made of bakelite, redmanol or thelike) each of which carries one of the circuit terminals andcontactfingers. For this purpose, I am 19 as respectivelyclamped to the twoinsulators 18 by. lock nuts 20,.each of these look nuts being threadedon a screw 21 which is threaded into thev adjacent insulator 18 axiallyof the latter. Each screw 21 also has a thumb-screw 22 threaded upon it,so that the end of one of the wires 23 can be The here showing resilientmetal contact fingers I clamped between these thumb-screws and theadjacent lock nut as shown in Fig. 2.

To cooperate with the two resilient fingers 19 which thus providecontact members respectively connected to the two wire terminals of thecircuit, I provide a contact bar 2 secured to an insulating block whichin turn is fastened to a rocking lever 26. This rocking lever 26 isdesirably forked and has each of its arms pivoted to one fork of thebase 17 of the switch as shown in Fig. 5. Then -I also provide suitablemeans for limiting the movement of the rocking lever in both directionsand for that purpose desirably provide a stop arm j 27 having aperforation through which the supporting stem 16 extends, thisperforation being elongated transversely of that stem (as shown in Fig.4) so that its end walls are adapted to engage the stem 16 for limitingthe movement of the rocking lever in both directions. The stop arm 27 isdesirably fastened to the insulator 25 conjointly with an eye 28 whichis connected by a tension spring 29 to the free end of the longer arm ofa bell-crank lever forming a portion of the throw-over connectionbetween the rocking switch lever and the plunger 7. This rocking leveris pivoted on an axis transverse of the axis of the plunger and parallelto the pivoting axis of the switch lever 26 and has its shorter arm 31extending over the top of the plunger 17, the free end of this shorterarm being connected by a tension spring 32 with some portion of thesupporting member-and desirably with a stiffening web 33 on the part 11.To provide for any adjustments which may be needed, I desirably pivotthe bellcrank lever on a support which is movable with respect to boththe supporting member of my appliance and the switch proper, and forthis purpose preferably employ a bracket 34 slidable 'upon thesupporting stem 16 and clamped in any desirable position on the latterby a screw 35. I also dejsirably do not have the shorter arm 31 of fthislever engage the plunger 17 directly,

but interpose a screw 30 threaded through this arm 31-,and having itstip in engagement with the plunger 17, this screw being latched in anyadjusted position by alock nut 37 Furthermore. I space the pivots of theswitch lever andof the bell-crank from the supporting rod 16 so that thelonger arm 30 of the bell-crank will swing past the plane connecting theaxis of the pivots 38 with that of the bell-crank pivot 38 during theswinging of the switching lever from its one extreme position to theother.

With the parts thus'arranged, it will be obvious from Fig. 6 that anupward flexing of the top of: the expansible receptacle 4 by an increaseof pressure within the latter elongating the spring 29 and causing thelatter to pull the rocking lever 26 from the position of Fig.2 to thatof Fig. 3. It therefore moves the contact bar 24 to the position inwhich it closes the circuit connection between the two contact fingers19. Likewise, when the pressure within the receptacle 4 falls, thesprings 32 and 9 will cooperate in causing the plunger to slide in. adirection away from the switch, and the spring willcause the bell cranklever to follow this movement by swinging in a clockwise direction. Assoon as the upper end of the long arm 30 has moved sutficiently, thespring 29 will throw the switching lever back to its off position ofFig. 2, thereby opening the circuit. By turning the bushing 10 in onedirection or the other, and by varying the resiliency of the springs 9and 32, I can readily adjust both the initial pressures and pressuredifferences at which the above described movements of the switchingmember will be effected, and by loosening the screws 35 and 40 I canreadily make such corresponding adjustments as may be needed in theposition of the switch and ofthe pivotal support for the bellcrank leverwhich forms part of the throwover mechanism.

In practice, I desirably employ sulphur dioxide as the expansible mediumwithin the receptacle 4 and the control tube 1 connected to the latterand I have found it practical to introduce this sulphur dioxide in sucha quantity that the pressure within the receptacle and tube will beapproximately or pounds per square inch at a surrounding temperature ofF. Then I adjust the various parts-of the mechanism so that the switchis in circuit-closing position with such a pressure in the controllingchambers. When the control tube is'coole to a temperature of 40 or lessby the resulting action of the refrigerator, a part of the inclosedgaseous sulphur dioxide is liquefied into a mist and the pressure withinthe control tube and the receptacle drops" accordingly, therebyoperating the switch although the pressure within these control chambersmay still be. considerably above that of the atmosphere. The circuit isthen opened automatically, thus stopping the operation of therefrigerator until the chamber housing the control tube 1 risessufficiently in temperature to evaporate the previouslyliquefied portionof the gas and restore the initial -pressure, whereupon thecorresponding expanding of the receptacle 4 actuates the plunger in theopposite direction and moves the switch back to its circuit-closingposition.

With such a charge of sulphur dioxide, I have found that by suitablyadjusting the various parts of the mechanism, Ican easily cause theswitch to respond to variations of less than 5 F. so as to maintain thetemperature within the refrigerator say between 36 and 40 F. .I havealso found that the presence of some air mixed with Sulphur dioxide doesnot materially afiect the operation at such a temperature range, so thatit is not necessary to exhaust the air from the receptacle 4 and thecontrol tube 1 before admitting the sulphur dioxide. However, theseportions may previously be exhausted if it is desired to employ my in-Vention for response to temperature variations in which the maximum islower than that above mentioned, and so that I do not wish to be limitedin thisrespect. Nor do I wish to be limited to the use of sulphurdioxide, as other gaseous mediums such as ammonia may be employed,provided that the metal parts are constructed of correspondinglysuitable materials.

Neither do I wish to be limited to the details of the switchingconstruction, throwover mechanism or other portions of the arrangementabove described, although I have found it highly advantageous to employinsulating switching portions afi'ording long leakage surfaces, togetherwith a self-cleaning switching arrangement and a triple adjustment forthe connections be-' tween the switch and the expansible casing.Obviously, all of these various features might be varied in many wayswithout departing fromthe s irit of my invention, so that I do not wishto be limited to the same, nor to the employment of all of the featuresin connection with each other or for the particular purpose aboverecited.

Furthermore, the location and position of my appliance may readily bevaried, as the same will operate equally well in vertical, horizontal orinclined positions, while the mounting of the cup 3 permitsthe controltube 1 to be swung about the axis of thiscup in any direction.

I claim as my invention 1. A pressure-responsive switch including anexpansible fluid container, a slidable stem bearing at one end againstand movable by the expansion of the container, a spring associated withthe stem for resisting movement thereof in one direction, a throw-overswitch including. a bell-crank lever having one arm connected to theswitch mechanism, a spring connected to the other arm of the lever, andan adjustable connection between the said other arm and the stem.

2. A pressure-responsive switch including 4 an expansible fluidcontainer, a slidable stem bearing at one end against and movable by theexpansion of the container, a spring associated with the stem forresisting movement thereof in one direction, a throw-over switchincluding a bell-crank lever having one arm connected to the switchmechanism, a spring connected tothe other arm of the lever, and a screwthreaded upon the said other arm of the lever and engaging the free endof the stem.

3. A pressure-responsive switch as per claim 1, in which both of thesaid springs resist a movement of the stem in response to an increase ofpressure in the container.

4. A pressure-responsive switch as per JOHN TWARDOWSKY.

